Preheat oven to 350 degrees and lightly grease a 9 x 13 baking dish with cooking spray.
Slice tomatoes (should have about 16 slices).
Layer tomato, slice of mozzarella and basil in the baking dish, alternating between red and yellow tomato slices.
Drizzle olive oil and balsamic vinegar on top.
Serve immediately.
Enjoy!